British experts scrambled on Monday to find the cause of an outbreak of foot and mouth disease while a drug company at the centre of the investigation said there had been no breach of its biosecurity measures.

Environment Secretary Hilary Benn said it was vital to contain the outbreak, which has infected a local herd of cattle and could cost the British livestock industry up to $30 million dollars a week in lost exports.

A laboratory run by Merial Animal Health Ltd, jointly owned by U.S. drugmaker Merck & Co. Inc and France's Sanofi-Aventis SA, said it stopped all production on Saturday, hours after cattle on a nearby farm were found to have an uncommon strain of the disease.

A nearby government-funded laboratory, around 5 miles (8 km) from the infected farm near Guildford, south-east England, was also closed and is under investigation.

Some 120 cattle have been slaughtered in a cull at the infected farm and of surrounding high-risk animals. Two animals have so far tested positive for foot and mouth and a spokeswoman for the agriculture ministry Defra said on Monday all the cattle that needed to be killed had been destroyed.

Prime Minister Gordon Brown, eager to be seen to be acting quickly against a backdrop of a devastating foot and mouth outbreak in 2001 when more than six million animals were slaughtered, has cut short his holiday and is chairing daily meetings of the government's crisis committee Cobra.

David Biland, managing director of Merial in Britain, said it was still too early to say what had caused the outbreak but insisted biosecurity procedures at the site were very strict.

Britain's chief veterinarian has ordered an urgent review of biosecurity measures at the sites, and Defra says "all potential sources" of the highly infectious virus are being investigated.

The head of the government-funded facility, the Institute for Animal Health, has said there was no breach of security at his laboratory and the suspect strain had not been used by his scientists for several weeks.

Benn said the government hoped to have an initial report from investigators at the Merial lab and the Institute for Animal Health within 48 hours.

"People are at the site working very, very hard to try and find out (what happened). We are not dealing with certainty here, but we have got the best people we can find doing the work and we will continue to follow the science at every stage," he told BBC radio. "The single most important thing we want is to contain this outbreak."

Attention focused on the labs as a possible source of the infection after Defra said the strain of virus confirmed in the cattle was not one "recently found in animals", but was a strain isolated 40 years ago by British biological researchers.


LAB STAFF TO HELP INVESTIGATORS

Merial, a leading animal health firm with 2006 sales of $2.2 billion, said its site "operates to the very highest international standards and we have complete confidence in the integrity of our operation here".

Biland said staff had been asked to come to work on Monday as normal. "The purpose of this is to make sure that every possible assistance is given to the investigation teams.

"Staff will be on hand to provide as much information as they can about the procedures for health and environmental protection, quality control, quality assurance and regulatory compliance," he said.

The European Commission said it had banned all live animal exports from Britain, as well as meat and dairy products from the infected area. Further restrictions could be brought in after EU vets meet on Wednesday.

Depending on how long the ban remains in place, the impact on British agriculture could be profound. Industry experts said British exports of livestock and meat were worth about 15 million pounds ($30 million) a week.

The foot and mouth crisis six years ago devastated British farming and hit tourism, costing the economy an estimated 8.5 billion pounds ($17 billion).